The present invention relates to vibrating beam gyroscopic apparatus that use the Coriolis acceleration which acts on a vibrating body when the latter rotates and is directed orthogonally to the rotational velocity and to the direction of vibration. It is particularly suitable for use as a rate gyro but may also be arranged for delivering a signal representative of an angle of rotation rather than of a rate of turn.
Numerous vibrating beam rate gyros have already been proposed. For example, a vibrating gyro having a H shaped resonator is described in EP-A-0 309 963. That gyro has four metal beams which carry driving piezo-electric elements for vibrating the beams in a first direction and sensing piezo-electric elements for measuring vibrations in a second direction, orthogonal to the first. Since the four beams make up the branches of an H-shape, the gyro can be secured via the junction between the two tuning forks constituted in this way since the junction which forms the cross bar of the H-shape constitutes a vibration node.
That disposition suffers from drawbacks. A twisting couple appears between the two tuning forks when the gyro is subjected to rotary motion. It is mechanically not convenient to support the vibrating unit by means of the cross bar of the H-shape. In practice it is not possible to give each tine or beam a cross-section that is square and is constant along its entire length and thus to obtain the same resonant frequency of vibration in the detection direction (output direction) as in the direction of the vibration caused by the driving elements (input direction).
Another rate gyro having a plurality of tines rectangularly shaped to provide for different frequences in the input direction and in the output direction is described in U.S. Pat. No. 3,127,775.